Essential oils are volatile oils obtained from plant or animal sources and are composed of complex mixtures of several constituents, such as monoterpenes and sesquiterpene hydrocarbons, monoterpene and sesquiterpene alcohols, esters, ethers, aldehydes, ketones, oxides and the like. These essential oils and their isolated constituents are frequently utilized as fragrance and flavor agents, and have been widely used in folk medicine for wound healing properties.
Scientific research has corroborated the beneficial effects of essential oils. Essential oils of eucalyptus have been found to “possess central and peripheral analgesic effects as well as neutrophil-dependent and independent anti-inflammatory activities” (Silva et al., 2003, J. Ethnopharmacol. 89(2-3); 277-283), and similar activity has been observed in essential oils from Lavendula angustifolia Mill. (Hajhashemi et al., 2003, J. Ethnopharmacol. 89(1):67-71). Essential oils have been demonstrated to exhibit antibacterial (Bezic et al., 2003, Phytother. Res. 17(9:1037-1040; Goren et al., 2003, Z. Naturforsch. 58(9-10):687-690; de Abreu Gonzaga et al., 2003, Planta Med. 69(8):773-775; Valero and Salmera, 2003, Int. J. Food Microbiol. 85(1-2): 73-81) and antifungal (Paranagama et al., 2003, Lett. Appl. Microbiol. 37(1):86-90; Shin, 2003, Arch. Pharm. Res. 26(5):389-393; Velluti et al., 2003, Int. J. Food Microbiol. 89:145-154) activities. Virucidal activity of essential oils has also been observed, including direct virucidal effects against Herpes simplex viruses types 1 and 2 (Garcia et al., Phytother. Res. 17(9):1073-1075; Minami et al., 2003, Microbial Immunol. 47(a):681-684; Schuhmacher et al., 2003, Phytomedicine 10:504-510).
Quaternary ammonium compounds (“QAC”) are a group of ammonium salts in which organic radicals have been substituted for all four hydrogens of the original ammonium cation. They have a central nitrogen atom which is joined to four organic radicals and one acid radical. QACs have a tendency to distribute to the interface of two phases (liquid-liquid or solid-liquid) to introduce continuity between the two different phases. QACs are known to have potent antimicrobial activity, capable of disrupting bacterial cell processes. QACs have been used as antiseptics, disinfectants, preservatives, biocides, etc.
Johnson et al. (U.S. Pat. No. 6,319,958 and US20020165130) relates to the use of sesquiterpenoids to promote uptake of exogenous antimicrobial compounds. Similarly, a related article discloses the use of sesquiterpenoids, such as nerolidol, farnesol, bisabolol and apritone, in enhancing bacterial permeability and susceptibility to exogenous antimicrobial compounds, suggesting that sesquiterpenoids have a non-specific and general effect (Brehm-Stecher et al. 2003, Antimicrobial Agents and Chemotherapy, 47(10):3357-3360). In particular, Brehm-Stecher et al. report that nerolidol, farnesol, bisabolol and apritone enhanced the susceptibility of S. aureus to the antibiotics erythromycin, gentamicin, vancomycin, ciproflaxin, clindamycin, and tetracycline. In addition, Brehm-Stecher et al. does not disclose the use of QACs as antimicrobial agents.
There is a continuing desire for an antimicrobial composition that is non-irritating, safe, and effective for repeated use in various professional and non-professional settings.